Trouble for Darwin’s Frogs

Chytrid fungus has likely driven the decline of two South American frog species named for Charles Darwin.

Nov 21, 2013

Abby Olena

R. darwiniiCLAUDIO SOTO-AZAT, ZOOLOGICAL SOCIETY OF LONDONBatrachochytrium dendrobatidis (Bd)—is a skin infection that killsamphibians around the world. Two affected species, Rhinoderma rufum and R. darwinii, are found in Chile and Argentina and called Darwin’s frogs, based on Charles Darwin’s involvement in their discovery. Scientists from England, Germany, and Chile have now shown that Bd was likely involved in the extinction of R. rufum and the decline of R. darwinii. Their work was published in PLOS ONE this week (November 20).

The researchers sampled for Bd in multiple species of wild amphibians in Rhinoderma native habitats in Chile and Argentina and preserved specimens in museums in South America and Europe. They found that all the Bd-positive archived amphibians had been collected in the 1970s, around the time that numbers of Darwin’s frogs began to decrease and that 12.5 percent of living amphibians in the Rhinoderma home range were infected. The scientists found no living R. rufum animals, which confirmed their conclusion—published this summer (June 12) in PLOS ONE—that R. rufum had gone extinct. Infection percentage in R. darwinii was close to 2 percent, which was much lower than the general amphibian population and suggested to the team that R. darwinii frogs may be highly susceptible to Bd and die quickly once infected.

Study coauthor Claudio Soto-Azat of Andres Bello University in Chile told LiveScience that habitat loss is also a probable reason for the decline of Darwin’s frogs.

“We can’t tell conclusively what has been causing the death of these frogs but we are putting together a powerful circumstantial case,” the London Zoological Society’s Marcus Rowcliffe, who did not participate in the research, told BBC News. “We ought to be extremely concerned.”